. These devices are also fantastic tool to probe validity of continuum mechanics 2 at atomic thickness 4,5 , study nonlinear dynamics 6,7 and gain deeper insight into quantum mechanics [8][9][10] . Among the 2D materials employed for fabrication of these devices, graphene has drawn the most attention and has been extensively studied [11][12][13][14][15][16][17] . Torr. Figure 2 shows the various resonant modes of the device detected using the three different transduction schemes. In addition to the mechanical resonance, we observe a number of electrical background peaks in 1ω and 2ω mixed down detection schemes. The peaks are identified as mechanical if nonlinear response is observed.For peaks below 100MHz, we are able to actuate the resonator deep into nonlinear regime in all the actuation schemes mentioned above. For peaks above 100MHz, Atomically thin suspended membrane fabricated using the so called -scotch tape method typically have large strain [11][12][13] . The strain affects the resonant frequency and nonlinear coefficients of the device and thus the nonlinear coupling between different modes of the device. To estimate the intrinsic strain of the device, we measured the frequency of 1 st mode of the device as a function of back gate voltage and calculated the intrinsic strain and mass loading on the device 17 (see figure S5). Based on the fitting of the experimental data the strain is estimated to be approximately 10 −2(assuming the device to be bilayer) at room temperature.Unlike the electrical measurements of graphene resonators reported to date, the ability to observe multiple modes and high strain makes it attractive to study nonlinear coupling between various vibrational modes. These devices can be driven into nonlinear regime by relatively modest electrostatic forces due to their atomically thin nature. Because of the presence of the electrostatic gate, the nonlinear driven resonant mode can be described by asymmetric Duffing oscillator equation given 5Where, is the damping ratio, 0 is the resonant frequency of the n th mode, α 2 and α 3 are the quadratic and cubic nonlinearity coefficients and F is the drive force. Figure 3a shows the response of the 1 st mode of device as the drive amplitude is increased. The initial Lorentzian shape is quickly driven to nonlinear regime with critical amplitude of about 7nm at dc gate voltage (V g DC ) of 15V (See figure S6).Beyond the linear regime, the device shows the hardening nonlinear response. coupling to other vibrational modes, we performed similar measurements on mode 2, 3 and 6 and found the coupling with mode 1 to be much weaker (see figure S8).We also observe strong nonlinear coupling between mode 4 and mode 5 resulting Conclusion:In conclusion, we demonstrate all electrical actuation and detection of atomically thinMoS 2 nanoelectromechanical resonator. Unlike previous reports with electrical measurements of such resonators, we are able to identify more than 10 mechanical modes. This is especially useful in resonators with length smaller than a ...

Nanomechanical resonators are used with great success to couple mechanical motion to other degrees of freedom, such as photons, spins, and electrons [1,2]. Mechanical vibrations can be efficiently cooled and amplified using photons, but not with other degrees of freedom. Here, we demonstrate a simple yet powerful method for cooling, amplification, and self-oscillation using electrons. This is achieved by applying a constant (DC) current of electrons through a suspended nanotube in a dilution fridge.We demonstrate cooling down to 4.6 ± 2.0 quanta of vibrations. We also observe selfoscillation, which can lead to prominent instabilities in the electron transport through the nanotube. We attribute the origin of the observed cooling and self-oscillation to an electrothermal effect. This work shows that electrons may become a useful resource for quantum manipulation of mechanical resonators. * These authors contributed equally to this work. 1 arXiv:1903.04892v1 [cond-mat.mes-hall]

Mechanical resonators based on a single carbon nanotube are exceptional sensors of mass and force. The force sensitivity in these ultralight resonators is often limited by the noise in the detection of the vibrations. Here, we report on an ultrasensitive scheme based on a RLC resonator and a low-temperature amplifier to detect nanotube vibrations. We also show a new fabrication process of electromechanical nanotube resonators to reduce the separation between the suspended nanotube and the gate electrode down to ∼150 nm. These advances in detection and fabrication allow us to reach displacement sensitivity. Thermal vibrations cooled cryogenically at 300 mK are detected with a signal-to-noise ratio as high as 17 dB. We demonstrate force sensitivity, which is the best force sensitivity achieved thus far with a mechanical resonator. Our work is an important step toward imaging individual nuclear spins and studying the coupling between mechanical vibrations and electrons in different quantum electron transport regimes.

Nonlinearities in nanoelectromechanical systems (NEMS) play a vital role in dynamics of the device. Clear understanding of nonlinearities and ability to tune and manipulate them to enhance the performance are crucial for applications with these devices. Here, we utilize an electrostatic mechanism to tune the geometric nonlinearity of an atomically thin NEMS. The exquisite tuning enables us to demonstrate hardening, softening, and mixed nonlinear responses in the device. The electrostatic tuning over the nonlinearity is utilized to effectively nullify Duffing nonlinearity in a specific regime. The observed mixed nonlinear response is the result of cross coupling between strong quadratic and quartic nonlinearities, an aspect explained by method of multiple scale analysis.

We report a high response optical detector based on n-ZnO/p-Si NWs core-shell arrays decorated with plasmonic Au nanoparticles (NPs), that works in the broad frequency range from UV (300 nm) to NIR (1100 nm) and consumes low power (few 𝜇𝑊). The optical detector combines the visible and NIR detectability of Si NWs with the UV detectivity of ZnO through the core-shell structure and broad band detectivity in the visible range has been achieved by decorating core -shell arrays with ligand-free Au NPs synthesized by using pulsed laser ablation in liquid. The photo-detector uses n-ZnO as the active photoconductive channel that is sensitive in UV region. However, using photo-gating as well as favourable band alignments the carriers generated at longer wavelengths in visible and NIR in Au NPs and Si NWs arrays were introduced into the conduction band of ZnO leading to its broad band performance. We observed significant enhancement of responsivity 𝑅 not only in visible range but also in UV and NIR region with a high detectivity of 10 11 (cmHz 1/2 W -1